Doctors Nadia Khan and Dr. Aman Nijjar with Dr. Davedeep Sohi have done research showing drastic differences among ethnic South Asians, ethnic Chinese and Caucasians in heart attack rates and outcomes at St. Paul’s Hospital.Photo by
Les Bazso

British Columbians of South Asian descent are far more likely to have heart attacks than Caucasians. This finding from St. Paul’s Hospital researchers illustrates one of several striking differences among ethnic groups with regard to heart attacks and death rates.

Ethnic Chinese have one-third the rate of heart attacks that Caucasians do.

The researchers have identified a number of risk factors such as diet and exercise habits, but puzzling paradoxes remain.

“We’re seeing that South Asians in general have about 50 per cent higher rates compared to whites,” says Dr. Nadia Khan, a St. Paul’s internist and associate professor of medicine at the University of B.C.

South Asians younger than 55 have double the heart-attack rate of Caucasians and 10 times the rate of ethnic Chinese. Diabetes — linked to poor diet and exercise habits — appears to be the underlying cause behind the high heart-attack rate among South Asians, say Khan and St. Paul’s internist Dr. Aman Nijjar, a clinical instructor at UBC.

Also, Nijjar says, South Asians have higher rates of abdominal obesity, and a lower threshold at which it contributes to blockages in the heart’s arteries.

Both ethnic South Asians and ethnic Chinese are less likely to exercise than the general population, Khan says. Although ethnic Chinese have much lower heart attack rates than South Asians, they are more prone to strokes, Khan says.

“It’s not clear why one group gets heart attacks and the other gets strokes,” says Khan, who is analyzing the types of strokes suffered by ethnic Chinese British Columbians.

The two ethnicities, however, are less likely than Caucasians to have chest pain with a heart attack. That symptom remains the most common among all ethnic groups, but 20 per cent of South Asians and Chinese under study haven’t presented with it, Khan says. Instead, they were having shortness of breath and profuse sweating.

“Public-health efforts should still focus on the most common symptoms of chest pain,” Khan says. “[But] we still need as doctors and patients to be alert that you can present with shortness of breath as well and sudden onset of sweating.”

The sooner after a heart attack that doctors unblock the heart artery, the less damage will occur to the heart. But ethnic Chinese and South Asians are more likely to delay seeking treatment after a heart attack, the researchers found.

“It’s probably that they don’t know what the symptoms are,” Khan says. “They don’t know that it’s an emergency. They might be waiting for a family member to come home. They might be waiting for the symptoms to go away.

“As soon as those symptoms start, you should call 911.”

Khan and Nijjar are studying patients in Vancouver and Fraser Valley hospitals to determine why members of the two ethnic groups tend to wait longer for treatment after a heart attack.

In spite of low rates of heart attacks among ethnic Chinese, the short-term outcome was significantly worse for that ethnic group than for South Asians and Caucasians. Twelve per cent of ethnic Chinese died within a month after a heart attack, compared to eight per cent for the two other groups.

Paradoxically, long-term outcomes favoured Chinese and South Asians — if they survived the first 30 days, they were living much longer than Caucasians. “The people that survived, they did really well,” Khan says. “That’s really perplexing.”

South Asians had a 35 per cent lower rate of mortality than Caucasians if they made it past 30 days, the researchers found.

The relative longevity for ethnic Chinese and South Asian heart attack patients came in spite of both groups being less likely than Caucasians to continue taking medications prescribed after their heart attack. “If they did take their medications, they probably would improve even more,” Khan says.

Khan and Nijjar believe heart-disease prevention needs to begin at an early age, and should start with early screening for diabetes and heart problems. Messages about healthy eating and exercise must be hammered in, they say.

“We need to start thinking about heart-health care outside of the doctor’s office,” Khan says. “We need to go to the workplaces, the schools, and communities to start promoting physical activity and diet and increased awareness.”

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